A variety of industries are subject to problems occurring with the growth of microorganisms including the leather industry, the lumber industry, the textile industry, the agriculture industry and the coating industry. In particular, biofouling, or biological fouling, is a persistent nuisance or problem in a wide varieties of aqueous industrial systems. Biofouling, both microbiological and macrobiological fouling, is caused by the buildup, of microorganisms, macroorganisms, extracellular substances, and dirt and debris. The organisms involved include microorganisms such as bacteria, fungi, yeasts, algae, diatoms, protozoa, and macroorganisms such as macroalgae, barnacles, and small mollusks like Asiatic clams or Zebra Mussels.
Another objectionable biofouling phenomenon, that of slime formation, occurs in aqueous systems. Slime formation can occur in fresh, brackish or salt water systems. Slime consists of matted deposits of microorganisms, fibers and debris. It may be stringy, pasty, rubbery, tapioca-like, or hard, and have a characteristic, undesirable odor that is different from that of the aqueous system in which it formed. The microorganisms involved in slime formation are primarily different species of spore-forming and nonspore-forming bacteria, particularly capsulated forms of bacteria which secrete gelatinous substances that envelop or encase the cells. Slime microorganisms also include filamentous bacteria, filamentous fungi of the mold type, yeast, and yeast-like organisms.
Biofouling, which often degrades an aqueous system, may manifest itself as a variety of problems, such as loss of viscosity, gas formation, objectionable odors, decreased pH, color change, and gelling. Additionally, degradation of an aqueous system can cause fouling of the related water-handling system, which may include, for example, cooling towers, pumps, heat exchangers, and pipelines, heating systems, scrubbing systems, and other similar systems.
Biofouling can have a direct adverse economic impact when it occurs in industrial process waters, for example in cooling waters, metal working fluids, or other recirculating water systems such as those used in papermaking or textile manufacture. If not controlled, biological fouling of industrial process waters can interfere with process operations, lowering process efficiency, wasting energy, plugging the water-handling system, and even degrade product quality.
For example, cooling water systems used in power plants, refineries, chemical plants, air-conditioning systems, and other industrial operations frequently encounter biofouling problems. Airborne organisms entrained from cooling towers as well as waterborne organisms from the system's water supply commonly contaminate these aqueous systems. The water in such systems generally provides an excellent growth medium for these organisms. Aerobic and heliotropic organisms flourish in the towers. Other organisms grow in and colonize such areas as the tower sump, pipelines, heat exchangers, etc. If not controlled, the resulting biofouling can plug the towers, block pipelines, and coat heat-transfer surfaces with layers of slime and other biologic mats. This prevents proper operation, reduces cooling efficiency and, perhaps more importantly, increases the costs of the overall process.
Industrial processes subject to biofouling also include papermaking, the manufacture of pulp, paper, paperboard, etc. and textile manufacture, particularly water-laid non-woven textiles. These industrial processes generally recirculate large amounts of water under conditions which favor the growth of biofouling organisms.
Paper machines, for example, handle very large volumes of water in recirculating systems called "white water systems." The furnish to a paper machine typically contains only about 0.5% of fibrous and non-fibrous papermaking solids, which means that for each ton of paper almost 200 tons of water pass through the headbox. Most of this water recirculates in the white water system. White water systems provide excellent growth media for biofouling microorganisms. That growth can result in the formation of slime and other deposits in headboxes, waterlines, and papermaking equipment. Such biofouling not only can interfere with water and stock flows, but when loose, can cause spots, holes, and bad odors in the paper as well as web breaks--costly disruptions in paper machine operations.
Sanitation waters, like industrial process waters, are also vulnerable to biofouling and its associated problems. Sanitation waters include toilet water, cistern water, septic water, and sewage treatment waters. Due to the nature of the waste contained in sanitation waters, these water systems are particularly susceptible to biofouling.
Liquid formulations, containing the microbicide 2-(thiocyanomethylthio)-benzothiazole (TCMTB), are known in the art and have often been used to control or prevent biological fouling, including biofilm and slime formation, in aqueous systems. TCMTB emulsifiable concentrates offer the advantage of easy application but suffer from disadvantages including strong skin irritation, freezing at cold temperatures, foul odor and precipitation of the active ingredient. Additionally, as concerns about environmental protection mount, efforts are being directed to reducing the volatile organic concentration (VOC) of biocides used in the treatment of industrial aqueous systems.
Solid formulations provide many advantages over liquid formulations. One such solid formulation is described in U.S. Pat. No. 5,413,795, incorporated by reference herein in its entirety. In U.S. Pat. No. 5,413,795, a solid TCMTB formulation was made having TCMTB adsorbed onto a water insoluble solid carrier.
Well formulated solid forms provide increased stability and reduce exposure to chemicals, solvents, or vapors. In a solid, different ingredients may be successfully combined where such a combination in a liquid might lead to unwanted reactions and potential loss of activity. Using a solid form, a chemical formulation can often be packaged and shipped in a more concentrated form than with liquid formulations. Solid forms are more easily contained within water-soluble packaging. Solid forms can also reduce or eliminate concerns regarding the liquid spilling or containers breaking during shipping or handling.
At the point of use, solid forms may also offer additional advantages over liquid formulations. Solid forms provide unit dosing and a uniform delivery system which aids in controlling the amounts used. Solid forms of water treatment chemicals can also be formulated to provide sustained or prolonged release of chemicals to the aqueous system.